RUI: Rearrangements in Dehydroannulenes and Polycyclic Aromatic Hydrocarbons

在美国国家科学基金会化学结构、动力学和机制项目RUI奖的支持下，旧金山大学的William Karney教授和Claire Castro教授将与本科生合作，利用量子化学方法研究碳氢化合物重排的机制。将要研究的碳氢化合物，脱氢环烯和多环芳烃（PAHs），具有很高的碳氢比，这使得它们对了解富碳分子的性质很有用。这种分子之所以吸引人，是因为它们有可能成为碳纳米管合成的前体。本研究将基本的有机化学概念与现代计算方法结合起来，阐明了从环境温度和亚环境温度下脱氢环烯的重排到非常高温（800°C）苯乙烯和相关系统的重排过程。pi先前的工作调用了新颖的拓扑结构（Möbius，双扭h<e:1> ckel），加上pi键移动，以解决环烯动态过程中长期存在的机制问题。pi和他们的学生现在将专注于将这一机制应用于脱氢环烯的顺反异构化，以确定：(1)所需键转移步骤的性质和拓扑结构，以及(2)累积烯在这种反应中是作为中间体还是过渡态。这些研究将阐明键转移作为构型改变途径的范围，并阐明分子内脱氢Diels-Alder反应。所产生的机理见解将有助于实验家在他们的合成中使用这种反应。此外，还将探讨苯环在苯环和其他体系中的收缩机理，以确定影响反应性的最重要因素。这项工作将确定最低能量的途径是否涉及碳烯或双自由基，并将澄清关键步骤是否协调或逐步。这些反应的势能表面映射将为从事碗形多环芳烃、富勒烯和碳纳米管合成的研究人员提供有用的信息。除了科学发现之外，本项目还将为本科生提供研究机会和培训，使他们接触到有机化学的最新主题，并为他们提供现代计算方法的实践经验，并帮助他们培养构建研究问题的能力。学生将在地区和国家化学研究会议上展示他们的成果。积极参与这项研究计划将为USF学生准备化学研究生学习或在化学行业就业。pi的研究团队始终反映了旧金山大学和湾区的多样性，他们的研究学生中有一半是女性。许多以前的小组成员已经进入化学工作队伍，或者已经进入化学研究生课程。学院将继续培训来自化学领域代表性不足群体的学生。最后，该奖项所带来的计算资源改善了大学的网络基础设施，并将提供给系里的其他研究小组。

With the support of a RUI award from the National Science Foundation's program in Chemical Structure, Dynamics and Mechanisms, Professors William Karney and Claire Castro at the University of San Francisco will work with undergraduate students to study mechanisms of hydrocarbon rearrangements using quantum chemical methods. The hydrocarbons that will be studied, dehydroannulenes and polycyclic aromatic hydrocarbons (PAHs), have high carbon-to-hydrogen ratios, making them useful for understanding properties of carbon-rich molecules. Such molecules are appealing because of their potential as precursors to the synthesis of carbon nanotubes. This research unites fundamental organic chemistry concepts with modern computational methods to elucidate processes from the rearrangements in dehydroannulenes at ambient and sub-ambient temperature to the very high temperature ( 800°C) rearrangements of phenylenes and related systems. Previous work by the PIs invoked novel topologies (Möbius, two-twist Hückel), coupled with pi-bond shifting, to solve longstanding mechanistic problems in annulene dynamic processes. The PIs and their students will now focus on the application of this mechanism to cis-trans isomerization in dehydroannulenes to determine: (1) the nature and topology of the bond-shifting steps required, and (2) whether cumulenes act as intermediates or transition states in such reactions. These studies will clarify the scope of bond shifting as a route for configuration change, as well as shed light on intramolecular dehydro Diels-Alder reactions. The mechanistic insights generated will be helpful to experimentalists using such reactions in their syntheses. Further, mechanisms for benzene ring contractions in phenylenes and other systems will be probed to identify the most important factors influencing reactivity. This work will determine whether the lowest energetic pathways involve carbenes or diradicals and will clarify whether or not key steps are concerted or stepwise. Potential energy surface mapping for these reactions will provide useful information to researchers engaged in the synthesis of bowl-shaped PAHs, fullerenes, and carbon nanotubes.In addition to the scientific findings, this project will provide research opportunities and training for undergraduates, expose them to current topics in organic chemistry, and give them practical experience in modern computational methods as well as help them develop the ability to frame research questions. Students will present their results at regional and national chemistry research conferences. Active participation in this research program will prepare USF students for graduate study in chemistry or for employment in the chemical industry. The PIs' research team consistently reflects the diversity of The University of San Francisco as well as that of the Bay Area, and half of their research students have been women. Many former group members have gone into the chemistry workforce or have matriculated into graduate programs in chemistry. The PIs will continue to train students from underrepresented groups in Chemistry. Finally, the improved computational resources enabled by this award enhance the university's cyberinfrastructure and will be available to other research groups in the department.